Saturday, December 26, 2015

PolitiMath from PolitiFact New Hampshire

PolitiFact New Hampshire, lately the Concord Monitor's partnership with PolitiFact, gives us a double dose of PolitiMath with its July 2, 2015 fact check of New Hampshire's chief executive, Governor Maggie Hassan (D).

Hassan was the only Democrat to receive any kind of false rating ("False" or "Pants on Fire") from PolitiFact New Hampshire in 2015. PolitiFact based its ruling on a numerical error by Hassan and added another element of interest for us by characterizing Hassan's error in terms of a fraction.

What type of numerical error earns a "False" from PolitiFact New Hampshire?

PolitiFact summarizes the numbers:

In her state of the state address, Hassan said that "6,000 people have already accessed services for substance misuse" through the state’s Medicaid program.

There is no question that substance abuse in the state is a real and pressing problem, and the statistics show that thousands have sought help as a result of the state’s expanded Medicaid program. But Hassan offered (and later corrected) a number that simply wasn’t accurate. The real total is closer to 2,000 -- about one-third the amount she cited.

We rate her claim False.

Describing Hassan's mistake as a percentage error using PolitiFact's figures, Hassan exaggerated her figure by about 230 percent. PolitiFact gave Hassan no credit for her underlying point.

In our PolitiMath series we found the closest match for this case from PolitiFact Oregon. PolitiFact Oregon said conservative columnist George Will exaggerated a figure--by as much as 225 percent by our calculations. The figure PolitiFact Oregon found was uncertain, however, so Will may have exaggerated considerably less using the range of numbers PolitiFact Oregon provided.

In any case, PolitiFact Oregon ruled Will's claim "False." PolitiFact Oregon gave Will no credit for his underlying argument, just as PolitiFact New Hampshire did with Gov. Hassan.

Percent Error and Partisanship

One of our research projects looks in PolitiFact's fact checks for a common error journalists make. We reasoned that journalists would prove less likely to make such careless errors for the party they prefer. Our study produced only a small set of examples, but the percentage of errors was high and favored Democrats.

PolitiFact New Hampshire's fact check of Gov. Hassan draws some consideration for this error, giving us the second mathematical element of note.

PolitiFact could have expressed Hassan's mistake using a standard percentage error calculation like the one we used. We calculated a 230 percent error. But PolitiFact New Hampshire did not use the correct figure (1,800) as the baseline for calculating error. Instead, the fact checkers used the higher, incorrect figure (6,000) as the baseline for comparison: "about one-third the amount she cited."

Using the number "one-third" frames Hassan's error nearer the low end. "One-third" doesn't sound so bad, numerically. Readers with slightly more sophistication may reason that the "one-third" figure means Hassan was off by two-thirds.

Sometimes using the wrong baseline makes the error look bigger and sometimes it makes the error look smaller. In this case the wrong baseline frames Hassan's mistake as a smaller error. The Democrat Hassan gains the benefit of PolitiFact's framing.